Muscular strength is developed and enhanced by the use of exercise apparatus. Traditional apparatus, such as dumbbells and barbells, have been used for progressive exercises. However, the use of such exercise apparatus carries hidden dangers when undertaken by the inexperienced person without proper supervision. For example, barbells present difficult balancing problems which increase the risk of serious injury.
More recently, various types of progressive weight training machines have been suggested to overcome problems inherent in the use of barbells and dumbbells. When first developed, such machines were of great height and bulk. In return for safety, these machines required substantially more floor space than was required for barbells.
Specialized weight lifting exercising apparatus have included components such as an upstanding frame having a track, one or more weights which may be selectively introduced, a trolley mounted on the track and operatively connected to the weights, and a means for applying force to lift the weights, such as a handle bar disposed outward from the trolley or a Latissimus or lat pull down bar connected to the trolley through a cable system.
In pulley-connected cable systems, the extent which a trolley may travel is limited by the height of the unit and by the height of the room in which the device is stored. Additionally, most pulleys require a top horizontal frame to provide a place where the pulley may be fixed. Thus, lateral space limitations also restrict pulley-connected weight lifting apparatus. Furthermore, the trolley of pulley-connected weight lifting apparatus often directs eccentric forces against the vertical frame. In pulley-connected exercise devices, eccentric forces which tend to destabilize the frame structure are imparted to the machine when a lifting force is applied and also when the user withdraws his controlled grip of the press bar or the lat pull down bar, removing any externally applied force.
Conventionally designed pulley-connected trolley systems have wheels affixed to the trolley which ride on the outer surface of guide rods or tracks and substantially surround the rod in order to resist and react to the eccentric forces. U.S. Pat. No. 1,114,458 to Friedli and U.S. Pat. No. 4,346,888 to Szabo are examples of such a trolley construction. At least three sets of wheels surround each track in these patents to oppose eccentric forces. Such design is complicated and costly to fabricate.
Alternatively, other exercise machines having a cable and pulley operatively connecting the trolley to the weight stack have trolley wheels contained within flanged channels or tracks. Examples include U.S. Pat. No. 1,905,352 to Porter, U.S. Pat. No. 3,807,728 to Chillier, and U.S. Pat. No. 3,635,472 (reissued as U.S. Pat. No. RE 28,066) to Walter Marcyan. Another example of a cable and pulley system exercise apparatus is U.S. Pat. No. 3,815,903 to Blomqvist. Such designs are difficult to fabricate. Additionally, the trolley wheels may bind or otherwise be captured while rolling within an enveloping trackway.
An alternative class of exercise machine which eliminates the necessity for a pulley and cable system is one having an upright supporting structure containing vertical tracks, a vertically reciprocative trolley mounted in and guided by the tracks, and weights supported in the upright structure connected directly to the trolley by means of a selector bar. A shoulder press or chess press handle bar may be connected to the trolley for imparting a lifting force. This single station class of exercise machine must cope with eccentric forces just as the cable and pulley system machines.
One variety of this selector bar connected trolley and weight stack exercise device has linear bearings forming an inner sleeve completely surrounding the guide rods. An example of such an apparatus is U.S. Pat. No. 4,470,596 to Desiderio. Other examples having separate linear bearing sleeves used for reciprocity of the trolley movement include U.S. Pat. No. 4,093,214 to Coker, et al., and U.S. Pat. No. 4,208,049 to Wilson. Each of these patents require special fabrication of a bearing for use within the body of the trolley. The constant motion of the trolley as it rides through vertical tracks increases the likelihood of wear and tear on the bearing members. Linear ball bearings are provided in U.S. Pat. No. 4,010,947 to Lambert, Sr. These ball bearings ride within the sleeves of the trolley body and completely surround the guide rods to offset all eccentric forces.
Linear bearing sleeves functioning to allow the trolley reciprocal movement along the guide rods require lubrication and maintainance. Being specially molded or fabricated, they are costly and of complicated design.
U.S. Pat. No. 4,354,675 to Barclay, et al. has at least four sets of opposingly disposed wheels fixed to the trolley to resist all eccentric forces. When a lifting force is applied to the trolley in Barclay, the upper rearward set of wheels and the lower forward set of wheels are pressed to the guide bar and resist the eccentric forces of lift. When the applied forces are released, the upper forward wheels and the lower rearward wheels engage the track. In U.S. Pat. No. 3,612,523 to Glynn, the lifting force is applied in a parallel but different plane from the trolley. Like Barclay, each trolley has four sets of opposingly disposed wheels. Both Barclay and Glynn require a minimum of four sets of wheels to resist all eccentric forces arising during exercise.
Trolleys requiring multiple sets of wheels, such as Barclay or Glynn, use these wheels to bear all eccentric forces. This increases the likelihood that the wheels will wear out quickly. A trolley-equipped exercise device should provide a better means for distributing the eccentric forces which arise during operation of the device.
In U.S. Pat. No. 3,912,263 to Yatso, and U.S. Pat. No. 4,317,566 to Uyeda, et al., the trolley wheels move within vertical tracks along an inner bar contained within the tracks. The guide tracks in both patents require channeled construction. In U.S. Pat. No. 4,200,280 to Goodwin, and U.S. Pat. No. 4,411,424 to Barnett, the channels are customized to surround and encompass the trolley wheels disposed within the channels. The flanges are of substantial depth to securely guide and direct trolley reciprocative movement. Such designs allow the trolley wheels to bind or otherwise drag against the channel walls.
U.S Pat. Nos. 3,971,555 and 4,199,139, both to Mahnke, disclose specially designed axle wheels which securely fit into a V-shaped, grooved, channelled guide track. The wheels disposed within such specially designed tracks require special fabrication and are costly to manufacture, produce, and replace. Wheels riding within a flange track may grab or bind the track, limiting the ability of the trolley to display smooth reciprocal motion. Also, the above-described devices are not useful for exercises using the lat pull down bar.